User's Manual Free ß - HCG Free beta hcg quantitative assay is designed for quantitative measurement of chorionic Gonadotropin free beta subunit in human serum. Catalogue Nr : KAPD1793 96 tests Revision Nr : 020812 8, rue de l Industrie B-1400 Nivelles Tel : +32.67/88.99.99 Fax : +32.67/88.99.90
Remark For in vitro diagnostic use only. Store at 2-8 C. INTRODUCTION Human Chorionic Gonadotropin (hcg) is a glycoprotein hormone normally produced by placenta during pregnancy. The hormone is present in blood and urine around seven to thirteen days following implantation of the fertilized ovum. Structurally intact hcg molecules consist of two non-covalently linked polypeptide subunits, the alpha and beta chain subunits. Measurement of intact hcg and of the alpha subunit of hcg appears to give similar results in blood and urine but not the levels of beta subunit. In normal second-trimester maternal sera, the level of intact hcg ranges from 20,000 mlu/ml to 50,000 mlu/ml. In contrast, the levels of either free α- or free ß-hCG are on average one half of 1% of hcg levels. hcg and the free subunits appear not to be useful as serological markers for nontrophoblastic tumors; however, the absolute increase of ß-hCG level in choriocarcinoma patients clearly differentiates it from normal pregnancy. Recent studies showed a significant increase in the level of free ß-hCG subunit in trisomy 21 cases as compared with controls. Hence it has been suggested that free ß-hCG subunit assay in a combination of maternal serum AFP could be effective in a screening protocol for trisomy 21. PRINCIPLE OF THE ASSAY The BIOSOURCE free ß-hCG subunit quantitative assay is based on the principle of a solid phase enzyme-linked immunosorbent assay (ELISA). The assay system utilizes a unique monoclonal antibody directed against a distinct antigenic determinant on the ß-subunit of the hcg molecule. Mouse monoclonal anti-ß-hcg antibody is used for solid phase immobilization (on the microtiter wells). A second monoclonal anti-ß-hcg antibody is in the antibody enzyme (horse radish peroxidase) conjugate solution. The test sample is allowed to react sequentially with the two antibodies, resulting in the ß-hCG molecules being sandwiched between the solid phase and enzyme-linked antibodies. After incubation (two separate 30 minutes incubations at 37 C), the wells are washed with water to remove unbound labeled antibodies. Then H 2 O 2 /TMB solution is added and incubated for 20 minutes, resulting in the development of a blue color. The color development is stopped by the addition of 2N HCL changing the color to yellow. The intensity of color developed is directly proportional to the concentration of ß-hCG in the serum. Absorbance is measured spectrophotometrically at 450 nm. REAGENTS Materials provided with the kit 1. Murine Monoclonal Anti-ß-hCG antibodies coated microtiter wells, 96 wells. 2. Enzyme Conjugate Reagent (18 ml): monoclonal anti-ß-hcg conjugated to horseradish peroxidase. 4. Reference Standard Set (lyophilized): 0, 2.5, 5, 10, 25 and 50 mlu/ml (calibrated against WHO IRP 75/551). 5. Solution A (13 ml): contains H2O2 6. Solution B (13 ml): Tetramethylbenzidine. 8. Stop Solution (2N HCL), 10 ml. Material required but not provided 1. Precision pipettes: 50 µl, 100 µl, 150 µl and 1 ml 2. Disposable pipette tips 3. Distilled water 4. Glass tubes or flasks to mix Color Reagents A and B 5. Vortex mix or equivalent 6. Absorbent paper or paper towel 7. Graph paper Revision Nr : 020812 Page 2/5
8. Microtiter plate reader (450 ± 10 nm) SPECIMEN COLLECTION AND HANDLING Collect blood by venipuncture, allow to clot and separate the serum by centrifugation at room temperature. If sera can not be assayed immediately, they can be stored at 2-8 C or frozen. This kit is for use with serum samples without additives only. STORAGE AND STABILITY OF KIT REAGENTS Store the kits at 2-8 C in a refrigerator. Keep microwells in a dry bag with desiccants. The reagents are stable until expiration of the kit. Solution A and B should be colorless; if solutions turn blue, they must be replaced. Do not expose these reagents to strong light during storage or usage. REAGENT PREPARATION 1. Before beginning the test. bring all samples and reagents to room temperature (18-25 C) and mix. 2. Standards: Reconstitute each lyophilized standard with 1.0 ml distilled water. Allow the reconstituted material to stand for at least 20 minutes and mix gently. Reconstituted standards should be stored sealed at 2-8 C. 3. H 2 O 2 /TMB Solution: To prepare H 2 O 2 /TMB solution, make a 1:1 mixing of Color Reagent A with Color Reagent B up to 1 hour before use. Mix gently to ensure complete mixing. The prepared H 2 O 2 /TMB reagent should be made at least 15 minutes before use and is stable at room temperature in the dark for up to 3 hours. Discard excess after use. ASSAY PROCEDURE 1. Secure the desired number of coated wells in the holder. 2. Dispense 50 µl of Standards, Controls, or Serum Samples into appropriate wells. 3. Dispense 100 µl of Zero Buffer into each well. 4. Thoroughly mix for 30 seconds. It is very important to mix completely. 5. Incubate at 37 C for 30 minutes. 6. Remove the incubation mixture by decanting or aspirating the contents. Rinse and wash the microtiter wells 5 times with distilled water. After the last wash strike the wells sharply onto absorbant paper to remove all residual water droplets. 7. Dispense 150 µl of Enzyme Conjugate Reagent into each well. Gently mix for 5 seconds. 8. Incubate at 37 C for 30 minutes. 9. Prepare H 2 O 2 /TMB solution up to 15 minutes before use. 10. Remove the incubation mixture by decanting or aspirating the contents. Rinse and wash the microtiter wells 5 times with distilled water. After the last wash strike the wells sharply onto absorbant paper to remove all residual water droplets. 11. Dispense 200 µl of H2O2/TMB solution into each well. Gently mix for 5 seconds. 12. Incubate at room temperature for 20 minutes. 13. Stop the reaction by adding 50 µl of Stop Solution to each well. 14. Gently mix for 30 seconds. It is important to make sure that all the blue color changes to yellow color completely. 15. Read optical densitiy at 450 nm with a microtiter well reader within 30 minutes. Revision Nr : 020812 Page 3/5
PROCEDURAL NOTE 1. It is very important to wash the microwells thoroughly and remove the last droplets of water to get the best results. 2. Pipet all reagents and samples into bottom of the well. 3. Absorbance is the function of the time and temperature of incubations. It is recommended to have all reagents and sample caps removed, all needed wells secured in holder and signed. It will ensure the equal elapsed time for each pipetting without interruption. CALCULATION OF RESULTS 1. Calculate the mean absorbance value (A 450 ) for each set of reference standards, controls and patient samples. 2. Plot the concentration (X) of each Reference Standards against its absorbance (Y) on full logarithmic graph paper. 3. Obtain the ß-hCG value of patient by reference to the standard curve. The BIOSOURCE ELIZA MAT 3000 Reader and the BIOSOURCE Regression Program allow the reading and computer assisted interpretation using a four parameter logistic function or cubic regression. LIMITATIONS OF THE PROCEDURE The results obtained from the use of this kit should be used only as an adjunct to other diagnostic procedures and information available to the physician. EXAMPLE OF STANDARD CURVE Results of a typical standard run with optical density readings at 450 nm shown in the Y axis against ß- hcg concentration shown in the X axis. This standard curve is for the purpose of illustration only, and should not be used to calculate unknowns. Each user should obtain his or her own data and standard curve. ß-hCG (miu/ml) Absorbance (450 nm) 0 0.021 2.5 0.122 5.0 0.247 10.0 0.573 25.0 1.662 50.0 3.231 EXPECTED VALUES AND INDICATIONS FOR QUANTITATIVE FREE ß-hCG ASSAY: 1. In early pregnancy, free ß-hCG concentration was found 10-80 mlu/ml. The free ß-hCG/intact hcg ratio was found 3.08-3.28 percents. After six to seven weeks the free ß-hCG and the ratio value declined. During the second and third trimester a constant ratio was observed about 1 percent. 2. Serum samples from 40 normal subjects were assayed, in this population, 99% of the values were less than 0.4 mlu/ml. 3. Serum hcg and free subunit levels in sera from patients with gestational choriocarcinoma were reported as following (12): Revision Nr : 020812 Page 4/5
From Ozuturk et al. Endocrinology, 1987. Patient hcg α-hcg ß-hCG no. (miu/ml) (miu/ml) (miu/ml) 1 210,000 112 8,000 2 22,195 20 1,300 3 6,840 1 232 4 36,000 44 3,900 5 4,200 2 350 PERFORMANCE CHARACTERISTICS Specificity Cross-reactivity was tested. Hormone Tested Color Intensity Produced Equivalent to ß-hCG (miu/ml*) hcg 1000 miu/ml 10 200 miu/ml 5 25 miu/ml 0 α-hcg 100 miu/ml 0 hlh 200 miu/ml less than 2 hlh 80 miu/ml 0 TSH 75 miu/ml 0 FSH 200 miu/ml 0 *ß-hCG 1mIU/ml = 1 ng/ml Sensitivity The minimal detectable concentration of ß-hCG in this assay is estimated to be 0.5 miu/ml. REFERENCES 1. Engall, E., Methods in Enzymology, volume 70, Van Vunakis, H. and Langone, J.J. (eds.), Academic Press, new York, 419-492 (1980). 2. Uotila M., Ripsöajto, E. and Engvall E., J.Immunol. Metods, 42, 11-15 (2981) 3. Brizot, ML, Jauniaux E. Mckie AT, Farzaneh F and Niclaides KH. Hum. Reprod. 1995; 10; 2506-9. 4. Forest JC, Masse J, Rousseau F, Moutquin JM, Brideau NA and Belanger M. Clin. Biochem. 1995; 28:443-9. 5. Breimer L. ann.clin.biocehm 1995:32:233. 6. Loncar K,Barnabei VM, and Larsen JW Jr. Obstet. Gynecol. Surv. 1995; 50:316-20 7. Densem J., and Wald NJ. Prenat. Diagn, 1995; 15:94-5. 8. Ozturk M, Berkowitz R, Goldstein D, Bellet D, Wands JR. Am J Obstet Gynecol 1988; 158:193-8. 9. Wald NJ, Cuckle HS, Densem JW, et at. Br Med J 1988; 297:883-7. 10. Hay DL. BR J Obstet Gynaecol 1988; 95:1268-75. 11. Macri JN. et al. Am J Obstet Gynecol 1990; 163:1248-53. 12. Ozturk M, et al. Endocrinology 1987; 120:499-508. 13. Cole LA. et al. Endocrinology 1983; 113: 1176 14. Gaspard UJ et al. Clin Endocrinol (OXF) 1980; 13:319. Revision Nr : 020812 Page 5/5